It has been suggested to deploy a supplemental inflatable restraint using a source of compressed gas, which compressed gas is released by a control signal activating an initiator. When the compressed gas is released, the gas flows out of its storage chamber to a supplemental inflatable restraint air bag to cause inflation of the air bag. Various publications show devices aimed at achieving these ends.
It has been suggested to implement a compressed gas supplemental inflatable restraint system as shown schematically in FIG. 1. Control module 10 controls and/or monitors the supplemental inflatable restraint system and typically includes a microprocessor 12. The deployment system includes a compressed gas source 18 comprising a chamber 20 in which compressed gas 22 is stored, typically at a pressure in the range of 1,000-4,000 pounds per square inch. The storage container 18 includes a pressure switch 24 located therein. Pressure switch 24 is a two-state switch responsive to the pressure of gas 22 within chamber 20 and is closed as long as the pressure of the compressed gas 22 is maintained above a threshold level. The threshold level is set as a system designer desires. Pressure switch 24 is opened when the pressure of gas 22 within chamber 20 falls below the predetermined threshold level. Two lines 14 (i.e., electrically conductive wires) couple pressure switch 24 to control module 10, allowing control module 10 to monitor the state of pressure switch 24. Two lines 16 are shown coupled to initiator 26, which typically comprises a squib and a combustible propellant that, when activated, provides an escape path for gas 22 from chamber 20 to air bag 28, allowing the gas to forcibly inflate air bag 28. When inflating, air bag 28 expands through cover door 30 and inflates in a manner well known to those skilled in the art. Through this manner of system control, four lines are required between the control module 10 and the deployment module 19. Two lines 14 allow control module 10 to monitor pressure switch 24 and two lines 16 allow control module 10 to control and monitor initiator 26.